1. Field of the Invention
The present invention relates to a video response testing apparatus in which coded signals can be displayed on the display screen of video display apparatus, eg., a television screen, and detected and decoded using a sensing probe. With such a system, coded signals can be applied to the picture of a television screen which can be arranged to be undecipherable when viewed by a person watching the television but which can be detected by a sensing probe handled by the person and then deciphered. In one application of this invention, the apparatus may be used, eg. as a teaching aid, to test the responses of a person viewing the television picture to questions displayed on the screen. For example, if a question is displayed in a multiple answer form, with each of a number of possible answers at different locations on the television screen, the sensing probe can be applied to a part of the television screen associated with a chosen one of the possible answers and arranged to react to coding on the screen to indicate whether or not that answer is the correct one.
2. Description of the Related Art
The specification of Canadian Pat. No. 948400 describes an apparatus of this general kind. In this specification, there is described an arrangement in which multiple answer questions displayed on the television screen can be flagged by respective coded patches. The television signal is arranged so that the coded patches flash in a manner indicative of whether the respective answer is correct or incorrect. The flashes are arranged so as not to be decipherable to the eye but can be decoded by a suitable probe handled by the viewer. In the Canadian example, the coding is done by arranging for the code patch on the screen to flash either an even number or an odd number of times to indicate a correct or incorrect answer respectively.
Such an arrangement as described in the Canadian specification has possible applications but also important limitations. The coding system described is very simple and also appears prone to possible errors, for example if one of a sequence of flashes is accidentally missed by the sensing probe so that the probe indicates a correct answer instead of a wrong answer, or vice versa. Furthermore the nature and content of the information supplied by the coded patches is very limited. Furthermore no details are given of how the system is to be put into practice.